Musnad Ahmad 1304:32

Ishaq ibn Yusuf narrated to us, he said: Sufyan informed us, from Layth, from Shahr ibn Hawshab, from Asma bint Yazid, she said: "Surah al-Ma'idah was revealed to the Prophet, may Allah bless him and grant him peace, all at once. It nearly broke the she-camel due to its weight."